Of all valvular heart lesions, aortic stenosis carries the worst prognosis. Within one year of diagnosis, approximately half of all patients with critical aortic stenosis have died, and by three years, this figure rises to approximately 80%. Currently, the most prominent and effective treatment for patients with aortic stenosis is aortic valve replacement via open heart surgery. Unfortunately, this procedure is a substantial and invasive undertaking for the patient.
While there have been significant advances in heart valve technology over the past 30 years, there has been little progress in the development of safer and less invasive valve delivery systems. Aortic valve replacement currently requires a sternotomy or thoracotomy, use of cardiopulmonary bypass to arrest the heart and lungs, and a large incision on the aorta. The native valve is resected through this incision and then a prosthetic valve is sutured to the inner surface of the aorta with a multitude of sutures passing only partly into the wall of the aorta. Given the current invasiveness of this procedure and the requirement to utilize cardiopulmonary bypass, aortic valve replacement surgery is associated with a high risk of morbidity and mortality. This is especially true in elderly patients, and in those patients who require concomitant coronary artery bypass grafting. Even when a good surgical result is achieved, virtually all patients require approximately 6 weeks to several months to fully recover from the procedure. In order to decrease these associated risks of aortic valve surgery, many have pursued novel approaches and technologies.
Less invasive approaches to aortic valve surgery have generally followed two paths.
In the 1980""s, there was a flurry of interest in percutaneous balloon valvotomy. In this procedure, a cardiologist introduced a catheter through the femoral artery to dilate the patient""s aortic valve, thereby relieving the stenosis. Using the technology available at that time, success was limited: the valve area was increased only minimally, and nearly all patients had restenosis within one year.
More recently, surgeons have approached the aortic valve via smaller chest wall incisions. However, these approaches still require cardiopulmonary bypass and cardiac arrest, which themselves entail significant morbidity and a prolonged post-operative recovery.
The ideal minimally invasive approach to the treatment of aortic valve disease requires aortic valve replacement without cardiopulmonary bypass and without cardiac arrest. Such an approach would greatly reduce patient morbidity and mortality and hasten recovery. Unfortunately, although there has been great progress in the treatment of coronary artery disease without cardiopulmonary bypass (e.g., angioplasty, with or without stenting, and xe2x80x9coff-pumpxe2x80x9d coronary artery bypass grafting), similar advances have not yet been realized in heart valve surgery. With an aging population and improved access to advanced diagnostic testing, the incidence and accurate diagnosis of aortic stenosis will continue to increase. The development of a system for xe2x80x9coff-pumpxe2x80x9d aortic valve replacement would be of significant benefit to this increasing patient population.
There are three important challenges to replacing a diseased aortic valve without cardiopulmonary bypass.
The first challenge is to remove the diseased valve without causing stroke or other ischemic events that might result from the liberation of particulate material while removing the diseased valve.
The second challenge is to prevent cardiac failure during removal of the diseased valve. In this respect it must be appreciated that the aortic valve continues to serve a critical function even when it is diseased. However, as the diseased valve is removed, it becomes acutely and severely incompetent, causing the patient to develop heart failure which results in death unless the function of the valve is taken over by another means.
The third challenge is placing a prosthetic valve into the vascular system and affixing it to the wall of the aorta. More particularly, during cardiac rhythm, the aortic and arterial pressures are substantially greater than atmospheric pressure. Therefore, any sizable incision made to the aorta in order to insert a standard valve prosthesis into the arterial system creates the potential for uncontrollable bleeding from the incision site. Furthermore, even if bleeding is successfully controlled, pressures within the aorta may result in weakening of the aorta caused by aortic wall dissection. In addition, large incisions on the aorta also increase the potential for liberating plaque from the aortic wall that can lead to embolic complications.
For these reasons, prior art valve prostheses potentially suitable for off-pump implantation have relied upon relatively flimsy expandable structures to support and secure the valve within the aorta. More particularly, these prosthetic valves are constructed so that they can be compressed to a relatively small dimension suitable for insertion into the arterial system, advanced to the site of the aortic valve, and then expanded against the aortic wall. Unfortunately, however, none of these relatively flimsy valve prostheses have proven adequate to endure the repetitive stresses undergone by the aortic valve over the ten to twenty years typically required.
In addition to the foregoing, the precise placement of such expandable prosthetic valves in the correct sub-coronary position can be extremely challenging, particularly in view of the high pressure, pulsatile blood flow passing through the aorta. Furthermore, expandable prosthetic valves would typically be positioned from a remote artery, which would reduce the ability to precisely control the placement and positioning of the device and therefore would increases the risk of obstructing the coronary arteries. The expandable prosthetic valves are held on the ends of elongate, flexible catheters that are threaded into the aorta, around the aortic arch and then expanded. The pulsatile flow during cardiac rhythm induces a to-and-fro motion of the valve prosthesis relative to the aorta that makes the timing of valve expansion critical for proper placement of the expandable prosthetic valve and hence the survival of the patient.
Finally, many of the challenges discussed in the foregoing section pertaining to aortic valve replacement are also relevant to other procedures in the aortic root such as aortic valve resection, aortic valve decalcification, stent grafting for aortic dissections, etc.
It is, therefore, one object of the present invention to enable the passage of a device from the left atrium, through the left ventricle, and into the arterial system.
Further, another object of the present invention is to enable the implantation of a device in the arterial system without cardiopulmonary bypass.
Further, another object of the present invention is to enable the implantation of a prosthetic valve in the arterial system without cardiopulmonary bypass.
Another object of the present invention is to allow the insertion of such a valve while minimizing the risks to the patient posed by large arterial incisions.
And another object of the present invention is to simplify the precise placement of such a valve.
Further, another object of the present invention is to enable the implantation of a device other than a valve, such as but not limited to a valve resection tool, a decalcifying tool, an aortic valve repair tool, or a stented aortic graft, in the arterial system without cardiopulmonary bypass.
Another object of the present invention is to allow the insertion of a device other than a valve, such as but not limited to a valve resection tool, a decalcifying tool, an aortic valve repair tool, or a stented aortic graft, while minimizing the risks to the patient posed by large arterial incisions.
And another object of the present invention is to simplify the precise placement of a device other than a valve, such as but not limited to a valve resection tool, a decalcifying tool, an aortic valve repair tool, or a stented aortic graft.
The present invention relates to a method and apparatus for positioning a device in the arterial system. More specifically, the present invention relates to a method and apparatus for positioning an aortic valve prosthesis in the aorta or aortic outflow tract, with or without cardiopulmonary bypass.
One aspect of the present invention is a method for deploying an aortic valve prosthesis. This valve prosthesis may include any of the known aortic valves including, but not limited to, stented and unstented bioprosthetic valves, stented mechanical valves, and expandable or self-expanding valves, whether biological or artificial.
In one aspect of the invention, there is provided a method of inserting a prosthesis or device from a lower pressure region into a higher pressure region of the cardiovascular system comprising the steps of: making an opening in a wall of a lower pressure region of the cardiovascular system; advancing the prosthesis or device through the opening and into the lower pressure region; and advancing the prosthesis or device through a natural barrier between the lower pressure region and the higher pressure region.
In another aspect of the invention, there is provided a method of inserting a prosthesis or device into a vessel within the arterial system comprising the steps of: making an opening in a wall of a low pressure region of the heart; advancing the prosthesis or device through the opening and into the low pressure region; advancing the prosthesis or device through a natural barrier between the low pressure region and the left ventricle; and advancing the prosthesis or device from the left ventricle into the arterial system and the vessel.
And in another aspect of the invention, there is provided a method of inserting a prosthesis or device into a vessel within the arterial system comprising the steps of: making an opening in a wall of the left atrium; advancing the prosthesis or device through the opening and into the left atrium; advancing the prosthesis or device through the mitral valve and into the left ventricle; and advancing the prosthesis or device from the left ventricle into the arterial system and the vessel.
And in another aspect of the present invention, there is provided a method for positioning a device in the arterial system comprising the steps of: making a first opening leading to the left atrium; passing a valve prosthesis through the first opening and into a cardiac chamber of the left side of the heart using a first manipulation instrument; making a second opening in the arterial system and advancing one end of a second manipulation instrument through the second opening and into the aforementioned cardiac chamber; securing the second manipulation instrument to the valve prosthesis; and then using the second manipulation instrument to retract at least some portion of the valve prosthesis out of the aforementioned cardiac chamber.
An alternative method for positioning a device in the arterial system comprises the steps of: making an opening leading to the left atrium; passing a valve prosthesis through the opening and into a cardiac chamber of the left side of the heart using an articulating manipulation instrument; using the articulating manipulation instrument to guide the valve prosthesis into the arterial cardiac chamber; releasing the valve prosthesis into a desired position: and then retracting at least a portion of the articulating manipulation instrument out of the aforementioned cardiac chamber and left atrium.
The pressure of blood flowing through the left atrium is very low, peaking at a few inches of water during the cardiac cycle. This pressure is a small fraction of that found within the arterial system and thus permits insertion of a conventional valve prosthesis through a relatively large opening formed in the wall of the left atrium without the risk of uncontrollable bleeding. In this respect it will be appreciated that various methods are known to those skilled in the art for controlling bleeding from an incision into the left atrium. The left atrium also rarely suffers from atherosclerotic plaque formation or calcification, thus minimizing the risk of embolic debris during such incision.
Another aspect of the present invention is the use of a prosthesis holding apparatus for releasably holding the valve prosthesis during manipulation to its implant site. The prosthesis holding apparatus may be secured to the prosthetic valve at any suitable location(s) through the use of any of a variety of approaches including, but not limited to, suture loops, barbs, hooks, grasping jaws, opposing magnetic poles, friction fits and the like. The prosthesis holding apparatus is configured to provides first and second manipulation mounts for engagement by the aforementioned first and second manipulation instruments, respectively, whereby the prosthetic valve can be delivered to its implant site. This construction is highly advantageous in that it permits the valve prosthesis to be passed easily and reliably from the first manipulation instrument to the second manipulation instrument within the vascular system.
In an alternative preferred embodiment, the prosthetic holding apparatus is attached on the ventricular side of the prosthesis. The aforementioned first manipulation instrument would articulate at or near the prosthetic valve to facilitate manipulation of the prosthesis holding apparatus (and hence the prosthesis itself) through the smallest possible incision site, then through the left atrium, the mitral valve and within the heart to align and position the prosthesis within the aortic annulus or left ventricular outflow track. In this alternative embodiment, there is no need for the aforementioned second manipulation instrument or the second manipulation mount.
In addition, if the prosthesis holding apparatus is attached on the aortic side of the prosthesis, the manipulation instrument may articulate and may be introduced into the arterial system, brought across the mitral valve into the left atrium, out the left atrium to pick up the prosthesis holding apparatus (and hence the prosthesis) and then retracted back to position the prosthesis directly into the aortic annulus without the need for another manipulation instrument.